The present invention relates to a mutual connection judging circuit for judging mutual connection of a device with an incorporated battery and a charger.
FIG. 2 is a diagram for explaining a conventional example of a mutual connection judging circuit. In the figure, {circle around (1)} represents a signal line for confirming the connection on charger side, and {circle around (2)} denotes a signal line for confirming the connection on device side. When a charger is connected with a device with an incorporated battery, for the purpose of starting the charging and terminating the charging by confirming the mutual connection or interconnection, it is necessary to judge full charging by the charging current and the charging voltage. However, when operating condition of the device is not confirmed, the charging current may be supplied from the charger while load current corresponding to various loading conditions is flowing. In this respect, it is difficult to judge or recognize the full charging, and it is not possible to control the starting and the termination of the charging. Therefore, for the purpose of recognizing the connection to the charger with the device and the stop operation of the device during charging operation, it is necessary to have two signal lines of {circle around (1)} and {circle around (2)} as shown in FIG. 2.
However, when the device with an incorporated battery is connected with the charger and the battery is charged if conventional mutual connection judging method as described above is used, the charger and the device judge the connection respectively via the signal lines {circle around (1)} and {circle around (2)}. In the one-sided detection of full charging by the charger, the detection itself is ambiguous and indefinite. As a result, charging may be performed beyond the limit, and this may impair the performance characteristics of the battery. Also, it is necessary to have two signal lines for mutual recognition of connection as shown in FIG. 2, and this means that there are many connection points and complicated structure is needed.
To solve the above problems, it is an object of the present invention to provide a mutual connection judging circuit for confirming mutual connection by a single signal line and for controlling connection signal from the device side.
To attain the above object, the present invention comprises a transistor on each of the charger side and the device side, a base of the transistor on the charger side is connected with a base of the transistor on the device side, and mutual connection is judged by collector potential of the transistor on the charger side and by collector potential of the transistor on the device side. In said circuit, a PNP transistor is provided as the transistor on the charger side, and charging is controlled by judging the mutual connection depending upon whether the collector of the PNP transistor is in opened state or not. Further, there is provided an NPN transistor as the transistor on the device side, and the device comprises a circuit for controlling emitter potential of the NPN transistor, said device turns on or off the NPN transistor by controlling the emitter potential depending upon whether the charging is in enable state or not, and said charger side starts the charging by judging collector potential of the PNP transistor.
Also, the present invention comprises a mutual connection judging circuit for judging mutual connection of a device with an incorporated battery and a charger, wherein said circuit comprises a transistor with a base thereof connected to a terminal for recognizing connection with the device and with an emitter thereof connected to a power source of the charger, and mutual connection is judged by detecting whether a collector of the transistor is in opened state or not. Said circuit comprises a transistor with a base thereof connected to a terminal for recognizing connection with the charger side, and with an emitter thereof grounded, and mutual connection is judged depending upon whether the collector of the transistor is in opened state or not. Further, there is provided a switching circuit for controlling the switching of the emitter of the transistor to grounded state or to opened state.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.
The invention accordingly comprises the features of construction, combinations of elements, and arrangement of parts which will be exemplified in the construction hereinafter set forth, and the scope of the invention will be indicated in the claims.